So I explored the Dim D with my DIY audio probe, and as stated in my comapct phasing post, it turns out the main problem lay with how I'd wired up the jacks. Once I'd sorted this out I got sound coming through fine... which is a big result.

However, the wet sound isn't very different to the bypassed sound at all...
slightly warmer is about all... and the rotary switch seems to have no noticeable effect... Am I right in thinking that turning the switch should make quite a noticeable difference?

I traced the sound across the boards and it makes it to the BBD board OK....
The MN3007 pins seem to make a mental bubbling sound, is this right?

Any ideas about where this could be going wrong, as I presume somethings not right?

So close but yet so far!!

Subtle is what it should be ... I think the original Dim D was always described as the one and only chorus device that just makes things warm, without sounding modulated ...

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

A very small one. Modulation Depth is slightly altered, and modulation rate is switched between 1 cycle per 2 seconds and one cycle per 4 seconds.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Cheers JH,
I think I just wasn't giving it a proper test and my monitor setup is very ad hoc and not ideal for listening to stereo effects.... Ive tried it on my headphones and it's much more obvious, and it's much mroe effective on certain sounds. I knew it was subtle, but I guess after the solina and tau I wasn't prepared for how delicate an effect it is... now I have got to grips with it though Im loving it already.
Thanks a lot.

Ok, I got the main board wired up and was just planning to check voltages and I'm getting +15VDC fine, but I'm getting around -28VDC. First, this probably means I got a resistor wrong around the LM337, right? And also, have I probably fried all the ICs and transistors on the board? God I hope not - I'm using HA1457Ws.

EDIT - Ugh, I see it - I put D15 in backwards. I'm such an idiot. I really hope I didn't fry all the chips that connect to the negative rail.

EDIT - Got the diode in correctly and now I'm getting -15VDC. Going to figure out if I destroyed anything tomorrow. Speaking of which, if I want to do so without hooking up the BBD board, I could hook up something to one of the inputs and see if I see the signal on the "send" pads, right? Then for the LFO chips I could check the LFO & Tau CVs pads, right? Does the middle pin of each Input header connect to the NC lug of the input Jack?

Ok, I got the main board wired up and was just planning to check voltages and I'm getting +15VDC fine, but I'm getting around -28VDC.

I don't want to sound overly pessimistic, but with -28V on the negative rail, it's likely that you fried every single IC on the board.

Quote:

if I want to do so without hooking up the BBD board, I could hook up something to one of the inputs and see if I see the signal on the "send" pads, right?

Right.

Quote:

Then for the LFO chips I could check the LFO & Tau CVs pads, right?

Yes, or just probe the IC pins directly.

Does the middle pin of each Input header connect to the NC lug of the input Jack?
[/quote]

In1 and In2?

Left pin is GND. The other two pins are + and - signal inputs (for blanced inputs). For unbalanced, or for testing, you just need one of them (middle or right) and leave the other one open, or tie it to GND.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

After looking at the datasheets last night I'm not very optimistic myself. I'm holding out hope for the HA1457s since it sounds like they're ok up to +-25VDC but I guess I'll find out tonight after work. It looks to me from the datasheets that all the transistors should be ok, including the power ones - would you agree?

Thanks for the input info. In my slightly frantic state forgot about the balanced input option.

Thanks again.

jhaible wrote:

numbertalk wrote:

Ok, I got the main board wired up and was just planning to check voltages and I'm getting +15VDC fine, but I'm getting around -28VDC.

I don't want to sound overly pessimistic, but with -28V on the negative rail, it's likely that you fried every single IC on the board.

Quote:

if I want to do so without hooking up the BBD board, I could hook up something to one of the inputs and see if I see the signal on the "send" pads, right?

Right.

Quote:

Then for the LFO chips I could check the LFO & Tau CVs pads, right?

Yes, or just probe the IC pins directly.

Does the middle pin of each Input header connect to the NC lug of the input Jack?

In1 and In2?

Left pin is GND. The other two pins are + and - signal inputs (for blanced inputs). For unbalanced, or for testing, you just need one of them (middle or right) and leave the other one open, or tie it to GND.

So from some preliminary tests it actually looks like things might be ok!!! I'm getting some LFO action from the LFO out and the Tau CV out, and the output of the Tau CV changes with the 2 Tau trimmers!! I also jumpered one of the sends to one of the returns and hooked up audio to input 1 and monitored from output 1 and I'm getting the audio signal and it sounds healthy! The only thing I'm a little curious about with the signal is that I'm feeding in a pulse wave directly from a VCO (0-5Vp-p) and what I see on the scope from the main board output doesn't look like a pulse wave exactly, but it sounds fine - is it normal that the circuit is probably effecting the waveform a bit?

Also it looked to me from the datasheets that all the transistors should be ok (including the power transistors) - would you think so as well? Not sure exactly what they do in this circuit - I know you mentioned something with oscillation related to the power transistors (I'm building a vintage version) and I'm not sure exactly how I'd know if any of the transistors in the circuit were fried (besides the ones for bypass of course).

So from some preliminary tests it actually looks like things might be ok!!! I'm getting some LFO action from the LFO out and the Tau CV out, and the output of the Tau CV changes with the 2 Tau trimmers!! I also jumpered one of the sends to one of the returns and hooked up audio to input 1 and monitored from output 1 and I'm getting the audio signal and it sounds healthy! The only thing I'm a little curious about with the signal is that I'm feeding in a pulse wave directly from a VCO (0-5Vp-p) and what I see on the scope from the main board output doesn't look like a pulse wave exactly, but it sounds fine - is it normal that the circuit is probably effecting the waveform a bit?

Also it looked to me from the datasheets that all the transistors should be ok (including the power transistors) - would you think so as well? Not sure exactly what they do in this circuit - I know you mentioned something with oscillation related to the power transistors (I'm building a vintage version) and I'm not sure exactly how I'd know if any of the transistors in the circuit were fried (besides the ones for bypass of course).

If it sounds good, don't worry about transistors. I guess they had some stress, but survived it!

Yes, waveform is changed with all the filtering that's going on in this device.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

It also appears bypass is working but I have 1 questions - I'm using a momentary N.O. stomp switch and the led only turns off while I'm holding the switch down - is this normal? The Compact Phasing project was the first (and only up until now) project I've built that had a remote bypass like this, of course that one stays in bypass mode, but I'm guessing that's because of the relay in that circuit, but just in case wanted to make sure this behavior I'm seeing with this circuit is correct - that you have to keep the switch held in the closed position for the effect to be bypassed - it won't latch bypassed without a mechanical toggle as you have in your wiring diagrams.

EDIT - just wired the main board to the bbd board for a Dim D configuration and there's definitely something wrong. I feed in a pulse wave and get no chorus, no matter where the switch is set - I hear just the pulse wave. What's strange to me is then I input a guitar and get a really unpleasant nasty distortion from the notes and it even breaks into just self oscillation at some point. When I play guitar through just the main board it sounds filtered as you mentioned but fine - none of the nasty distortion or oscillation. I'm going to start tracing the signal path on the bbd board this weekend but wondering if you had any ideas what the culprit might be based on the odd behavior I'm getting with a guitar signal.

It also appears bypass is working but I have 1 questions - I'm using a momentary N.O. stomp switch and the led only turns off while I'm holding the switch down - is this normal? The Compact Phasing project was the first (and only up until now) project I've built that had a remote bypass like this, of course that one stays in bypass mode, but I'm guessing that's because of the relay in that circuit, but just in case wanted to make sure this behavior I'm seeing with this circuit is correct - that you have to keep the switch held in the closed position for the effect to be bypassed - it won't latch bypassed without a mechanical toggle as you have in your wiring diagrams.

EDIT - just wired the main board to the bbd board for a Dim D configuration and there's definitely something wrong. I feed in a pulse wave and get no chorus, no matter where the switch is set - I hear just the pulse wave. What's strange to me is then I input a guitar and get a really unpleasant nasty distortion from the notes and it even breaks into just self oscillation at some point. When I play guitar through just the main board it sounds filtered as you mentioned but fine - none of the nasty distortion or oscillation. I'm going to start tracing the signal path on the bbd board this weekend but wondering if you had any ideas what the culprit might be based on the odd behavior I'm getting with a guitar signal.

Thanks.

Krautrock Phaser: One short push on the switch will turn the LED on, the next short push on teh switch will turn it off.

Subtle Chorus: Did you have the BBD board connected to the main board when there was that negative overvoltage?

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Krautrock Phaser: One short push on the switch will turn the LED on, the next short push on teh switch will turn it off.

Right, and by contrast the Dim-D bypass does not work this way, correct?

jhaible wrote:

Subtle Chorus: Did you have the BBD board connected to the main board when there was that negative overvoltage?

No, fortunately it was not connected - I'm working on adding 1 board at a time and checking that each minimal configuration seems to work first so I only had the main board wired up when that diode was soldered in the wrong way.

Krautrock Phaser: One short push on the switch will turn the LED on, the next short push on teh switch will turn it off.

Right, and by contrast the Dim-D bypass does not work this way, correct?

Right.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

This morning I hooked up a sine wave individually to each BBD line directly to the BBD board input pads (the signal didn't run through the main board at all) and actually everything seemed to look ok on the scope with the exception of possibly 1 thing - on each BBD channel, the signal coming directly out of the BBD chip looked a little smeared, like when you see HFO around an op-amp. I'm assuming this is just from the BBD chip doing its thing, especially since I see the same thing on each channel, but wanted to make sure.

This morning I hooked up a sine wave individually to each BBD line directly to the BBD board input pads (the signal didn't run through the main board at all) and actually everything seemed to look ok on the scope with the exception of possibly 1 thing - on each BBD channel, the signal coming directly out of the BBD chip looked a little smeared, like when you see HFO around an op-amp. I'm assuming this is just from the BBD chip doing its thing, especially since I see the same thing on each channel, but wanted to make sure.

Some remains of the clock frequency is to be expected. Can be minimized with R24 and R65.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Ah ok that's what that is. I've figured out the bbd board isn't the problem it's the main board. It does pass audio but also is producing some motorboating noises even with no audio input. Any ideas? I would think if any of the chips were fried i wouldn't hear audio at the output though looking more closely at the audio at the output it doesn't look quite right.

EDIT - I'm an idiot again. I was tracking down some HFO around the chips for U8 and as I was looking at the board I saw 2 empty sets of pads for the 100pf bypass caps - no wonder I'm having these issues. Hopefully this will take care of all the problems.

Despite my best efforts at sabotaging this project I now have successfully tested both Dim-D and Dim-T modes! Waiting for my panel to wire it up Dim-TD style but happy to have everything seemingly working!

Despite my best efforts at sabotaging this project I now have successfully tested both Dim-D and Dim-T modes! Waiting for my panel to wire it up Dim-TD style but happy to have everything seemingly working!

Congratulations!

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Despite my best efforts at sabotaging this project I now have successfully tested both Dim-D and Dim-T modes! Waiting for my panel to wire it up Dim-TD style but happy to have everything seemingly working!

I finished wiring up the full switchable Dim-TD today and now I'm getting a loud electrical hum from the Dim-T mode. Interestingly when I connect the ground clip of my scope probe to the ground lug of any of the input or output jacks (on the main board) the humming goes away. Does this mean I need some shielded cables somewhere on the Tau board connections? I looked at the Tau docs and the only shielded cable you suggest there that would apply for the Dim-T is the input wires, but when I first tested Dim-T mode the input wires were the same length they are now and I did not have this issue. The output wires are twice as long now that they are wired up through the Dim-TD switch - could this be a problem? Any thoughts/suggestions much appreciated.

I finished wiring up the full switchable Dim-TD today and now I'm getting a loud electrical hum from the Dim-T mode. Interestingly when I connect the ground clip of my scope probe to the ground lug of any of the input or output jacks (on the main board) the humming goes away. Does this mean I need some shielded cables somewhere on the Tau board connections? I looked at the Tau docs and the only shielded cable you suggest there that would apply for the Dim-T is the input wires, but when I first tested Dim-T mode the input wires were the same length they are now and I did not have this issue. The output wires are twice as long now that they are wired up through the Dim-TD switch - could this be a problem? Any thoughts/suggestions much appreciated.

Does connecting the Dim TD output to a grounded (earth ground) input help?

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

I finished wiring up the full switchable Dim-TD today and now I'm getting a loud electrical hum from the Dim-T mode. Interestingly when I connect the ground clip of my scope probe to the ground lug of any of the input or output jacks (on the main board) the humming goes away. Does this mean I need some shielded cables somewhere on the Tau board connections? I looked at the Tau docs and the only shielded cable you suggest there that would apply for the Dim-T is the input wires, but when I first tested Dim-T mode the input wires were the same length they are now and I did not have this issue. The output wires are twice as long now that they are wired up through the Dim-TD switch - could this be a problem? Any thoughts/suggestions much appreciated.

Does connecting the Dim TD output to a grounded (earth ground) input help?

JH.

If the amp I'm connecting the output of the Dim TD to has a 3-prong power cable can you assume the inputs are grounded to earth ground? If so (or if you might know if my Mackie mixer would probably have or probably not have earth grounded inputs) then I was still getting this hum when connecting the Dim TD directly to my mixer and monitoring directly from the mixer through headphones.

I don't know - grounding stuff is complex, and full of surprises.
But I'd say if you only get that hum without any GND attached (Scope probe is grounded, I presume), a GND connection is what you need, and there's probably nothing wrong with the circuit.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

I played around with it a little more last night and magically this overbearing noise just cleared up. There still is some high pitched noise I can hear with the phasing but this seems like normal Tau noise (unless in this circuit the NE570 is supposed to squash that?). Could this be an issue with the DC power lines running too close to the APF circuits on the Tau boards? Didn't seem to make a difference either way when I would move the power cables around. Anyway, hopefully it won't happen again.

Another question - I have decided to go with balanced inputs and outputs. I am unclear on how (or if) I could add an input attenuator. The first thing that comes to mind is a 4-gang pot, but even if I could find one, I've read that using pots with balanced signals is discouraged for risk of disrupting the balance of the signal. Do you have any suggestions? Sounds like shunt attenuators are recommended but the only DIY one I could find is very expensive. Not a huge deal if I can't include one - the only reason I'm being a little stubborn about it is I had a panel made that has a hole drilled and labeled for an input attenuator (oops).

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